The invention relates to a storage head for a blow molding machine for the discontinuous production of plastic hollow bodies, comprising at least one extruder, connected to the storage-head housing, for feeding at least one liquid plastic melt into the storage head; a centrally disposed shaft; and a distributor element, formed as a spiral channel and enclosing the shaft concentrically, to distribute the plastic melt over a circular circumference and conducting it into an annular storage space underneath the ejector piston, which is mounted in the storage-head housing so as to be movable axially, and by means of which the plastic melt stored in the storage space can be ejected by an annular nozzle gap which connects underneath to the storage space.
A comparable storage head is previously known, e.g., from the DE-OS 30 00 444, and is described in detail there. The spiral-channel distributor to distribute the liquid plastic melt is here disposed on the outside wall of the ejector piston. The spiral-shaped channel is supplied with liquid plastic melt through two axial grooves that are disposed in the outside wall of the ejector piston above the spiral channel. These axial grooves are connected to appropriate radial borings in the storage housing so as to feed in material from the extruder. A disadvantage here is that, when the plastic is distributed over the circumference, such that the storage space is filled up and the ejector piston moves slowly and steadily into its upper ejector position, the spiral-channel distributor is bounded by two outside walls that move relative to one another, and the inflowing plastic material is constantly subject to a shear effect. Furthermore, during the ejection process, there is no defined ejector edge present at the outside circumference of the ejector piston, so that the entire plastic ring column in the storage space adheres on its outside to the inside wall of the storage housing and is not ejected uniformly over the entire cross-section but rather is displaced to the outside in the manner of a wedge, adheres to the storage housing, and is sheared off or smeared off. This causes undesirable material displacements and excessive internal friction as well as a non-uniform pressure build-up within the liquid melted plastic material. The result is a disturbed layer build up in the hose-shaped parison that is ejected through the annular-gap nozzle of the storage head, or in the blown plastic hollow body or in the end product.
These disadvantages should be avoided.